Symbiotic Desire
by Serfius
Summary: The Prothean's did more than just observe Humanity's early stages, they influenced it. They hoped to transform the Human's into their weapon to fight the Reapers, but were unable to accomplish their goal. But they managed to leave something behind that may just help them to survive their own cycle. [Summary, Title, and Ratings subject to change]
1. Prologue - The Last Martian's Gambit

**Alright, let's do some trailblazing! The very first Mass Effect/Guyver crossover, at least on this site! I'm very curious to see how this fic will do. In my experience The Guyver isn't that popular of a franchise, but it was my very first anime that I ever saw (The gruesome scenes were pretty scary for child me, but I still liked the show.) and it's been something of a favorite ever since!**

**Warning(s)!: This fic will probably be the least of my priorities in actually writing, so updates will likely be very slow. Pretty much I'm just releasing this now so that word can start spreading about it, so to speak.**

Disclaimer: I do not own either Mass Effect or The Guyver. I am writing this purely to see reader reaction and for fun. I make no financial profit doing this.

Prologue – The Last Martian's Gambit

Alarms blared throughout the Prothean Observation Outpost turned Bio Weapons lab. The Reapers had finally forced their way to this planet, after dozens of years of war.

Korai Irikan, the commander and lead scientist of the outpost, raced to the depths of the facility as fast as he could, shouting orders to his staff. In his arms he clutched the culmination of his life's work, a weapon that could have helped them win the war. But the Reapers found them too soon for their work to come to fruition.

"Release the Zoanoids! Unleash them on the Reaper forces!" The building shook around him, nearly making him fall.

* * *

"Right away sir!" A scientist in their genetics labs responded, looking at the immature results of their experimentation. A series of monitors showed multiple large cells that held what could only be described as monsters. Large bipedal creatures, nearly twice the size of any Prothean, with patchy grey fur, sharp teeth, and tight, corded muscle. Not for the first time the Prothean wondered if they'd be punished for their actions in the afterlife. The beasts used to be inhabitants of the third planet in this system, before they'd been captured by the Prothean's and brought here for experimentation.

The war against the Reapers had been raging for longer than any Prothean here had even been alive, and their armies were mere shadows of what they had been. So Doctor Irikan had come up with a plan to reinforce their armies, by manipulating the genes of a primitive race into cheap, powerful, and obedient shock troopers.

The inhabitants of the third planet were a fortuitous find, possessing multiple qualities they had been looking for. They were intelligent, capable of forging and using tools. They had a high aptitude for violence, slaying beasts that should have been able to easily slaughter them. They were very adaptable, capable of living and thriving in a wide array of environments. But most interesting was their genetic diversity, making it very easy to augment and manipulate their genes into a desired form.

Eventually they had been able to build in a battle form, directly into their genetic code, what they were calling a Zoanoid. But their studies were incomplete. They had wanted to create multiple Zoanoid types, for the different theatres of war; tailor their design so they could take full advantage of and thrive in specific battlefield types. They had been so _close!_ Perhaps one more month and they would have had the first wave ready to deploy, but the Reapers had broken through!

Quickly pressing a series of buttons and inputting his pass code, the doors to the Zoanoid's cell's slid open. The creatures inside didn't hesitate to escape, and it didn't take long for them to come across Reaper forces, the monstrosities the Reapers had transformed their captured brothers and sisters into. They realized their hypocrisy, transforming another race into bio weapons to fight the Reapers, but they were desperate.

The Zoanoid's great strength allowed them to tear apart any Reaper soldier they got their clawed hands on, and their speed was enough to ensure their targets wouldn't get away, but they had no defense against their guns. The particle weaponry easily sliced through their toughened hide, but it didn't matter. The Zoanoids were serving their purpose, buying time for Irikan to secure his work for the next cycle to discover, and hopefully help them defeat the Reapers.

The blast doors to the lab began to spark as the Reaper forces began cutting through the thick metal. When the attack had begun, the science team had sealed themselves inside, severing all controls to the blast door. The only way to open it would be through force.

The Protheans all readied their particle rifles, taking cover behind overturned exam tables and counters, ready to fight to their dying breaths.

* * *

Korai reached the stasis capsule, out of breath. Setting the case containing his work down on a nearby table, he opened it for one last look at his creation. Inside were three thick disc like objects. They were fleshy tendrils encased in metal plates with a silvery orb in the center. He called them Guyver Units, meant to be joined with their test subjects as a weapon. Unfortunately, the potential for a Prothean was negligible, a mere small boost to physical ability. But tests with the third worlds species had been promising, magnifying their abilities tremendously for a brief period until the unit malfunctioned and killed the test subject. The three units he had here were the perfected model. There should be no lasting harm to the host no matter how long the unit is active.

Resealing the case, he placed it reverently into the stasis capsule, and locked it shut, engaging the transit system that would take it deep beneath the facility, where their backup servers were in hibernation, now completely cut off from any activity above.

Moments later, he could hear the scuttling of the Collectors chitin covered limbs moving down the hallway. Reaching into a pocket, Korai withdrew a simple cylindrical detonator, and flipped open the safety guard. Just as the Reaperized Protheans reached him, pointing their guns threateningly, he smirked savagely and pressed the button.

"This is one Prothean you will not take, dead or alive! I will take all of you to hell with me!"

The upper levels of the outpost erupted in nuclear fire, obliterating everything in a mile radius, but leaving the lowest levels intact. Deep beneath the ground the stasis capsule safely cradled the Martian's gambit, waiting to be discovered.

* * *

**End Prologue!**

**Ok, so let's see how that goes. As the character filter says, this will be a femshep fic, who will be Earthborn and primarily Paragon, though there'll probably be times when Renegade action is taken. As for pairings, I don't know yet. But not Kaiden, as I just don't really like him.**

**Anyways, please review and let know your thoughts! All feedback, constructive criticism and questions are welcome and appreciated!**


	2. Chasing Opportunity

Disclaimer: I do not own either Mass Effect or The Guyver. I am writing this purely to see reader reaction and for fun. I make no financial profit doing this.

Chapter 1 – Chasing Opportunity

**CE 2172, April 11th – New York Junkyard – 1:34 AM**

"You know," A copper haired eighteen year old girl grunted out, prying open an old server box, crouched atop a small hill of cracked and broken metal and electronics. "It wouldn't hurt if you could, you know, _help_ me look!" She wore a faded red hoodie zipped up halfway over a dirty white t-shirt and baggy blue jeans, all ragged and beginning to fall apart. A few moments of jiggling her screwdriver under the plate had the rusted case popping open with a slight screech. Tucking the screwdriver into the backpack next to her, she pulled out a small, battered flashlight that projected a beam so weak it was nearly useless.

"I would, but the thing is I have no idea what you're looking for Jane!" A black haired sixteen year old boy of Asian descent called up to her. He wore a burgundy vest over a black long sleeved shirt and a pair of jeans with the knees worn off, all in a similarly ragged condition as his companions. "I'm just here to make sure you don't get into any trouble. Or at least make sure you get _out_ of it in one piece."

Jane rolled her eyes as she examined the chips and circuitry in the server case, tossing whatever was beyond salvaging over her shoulder and pocketing what she liked. "Seriously, I've done this a million times Leng, I've got it down pat! The piece of shit they call a security system is so easy to hack I could've done it in my sleep!" If by hack you meant unplugging a few loose wires and killing the power.

"You know that's not what I was talking about. The Blue's are known to wander around here from time to time and they'd love nothing less than to catch a Red alone out here." The Blue's were one of the many street gangs around, none of whom got along particularly well. The stupid bastards weren't even creative enough to come up with their own name, just ripping off the Tenth Street Reds since they didn't have the imagination necessary to come up with their own identity.

Jane let the case fall shut and shoved it away from her, moving on to the next discarded computer, having a much easier time prying this one open. "I've almost got everything I need to get my laptop running again, ten more minutes, promise." The damn, stubborn thing had been with her for the last seven years, and it was about ready to shatter after everything she'd put it through, held together by a lot of duck tape and some haphazard self taught engineering. What she wouldn't give for one of those omnitools she saw everywhere. But, if the next few days panned out like she hoped, she'd soon have one of her own and be done with the gang life for good! Jane let out a triumphant cry as she spotted the last piece she needed, and pulled the relatively good motherboard out of its slot. "Nice! This'll do the trick." She eagerly packed her spoils away into her backpack, pulled the straps over her shoulders and made her way back to where Leng was waiting.

"Can we go now?"

Jane nodded, leading them back out of the junkyard the way they'd come in, plugging the security system back in. If they didn't want people sneaking in like they'd just done, they should really do better at securing their wiring.

"So you're really gonna sign up with the Alliance?" Leng asked her as they walked down the sidewalk, streetlamps flickering overhead.

"Damn straight I am." Jane nodded with a determined glint in her emerald eyes. As of an hour and a half ago, she was officially eighteen years old, meaning legally an adult and therefore eligible for military service. "I can hardly wait! No more scavenging, begging or stealing creds or half rotten food, no more drafty apartment shared with a bunch of stinking creeps, no offense," She shot a wry smile at him as he shrugged indifferently. It couldn't be denied that there was something left to be desired when it came to the hygiene of the gang members they shared a living space with. "The Alliance will give me everything I need and more." Free room and board, wide array of healthcare and benefits, and a steady paycheck; all on the Alliance's dime. "Heck, maybe I'll even get optimized for a Zoanoid form." She grinned, only half joking. You had to be something special to be selected for optimization; not just anyone got to be a Zoanoid.

The discovery of the Prothean ruins on Mars in 2148 had been huge. In addition to element zero and a cache of Prothean tech that shot Humanity's technology several centuries ahead, scientists had found still functioning databanks deep beneath the Martian surface. After a few months of study they'd eventually come across a hugely startling secret. Apparently the Protheans had been rather interested in humanity's ancestors, tampering and experimenting with their genetic code. They'd found multiple templates for transformations humans could make with the proper treatments, what they learned were called Zoanoids. According to the data found, these forms granted a great deal of strength and endurance to the subject, vastly improving their odds of survival in hazardous conditions. Eventually it had been decided to look into adapting this research for modern human use, and shortly thereafter the first Zoanoids were created, restricted to Systems Alliance military control.

At first the whole idea had been wildly unpopular, due to the Zoanoids intimidating, monstrous looks, but slowly public opinion shifted as the benefits became apparent coupled with strict psychiatric evaluations of those who volunteered for the process. It was also quite helpful that these transformations were not permanent, the subjects capable of voluntarily shifting between their normal Human form and their Zoanoid forms at will. But the turning point that seriously shifted public opinion in favor was the First Contact War in 2157, where the Zoanoid's distinguished themselves as highly valuable assets on the battlefield, tearing through invading Turian forces. Since then, humans have become rather comfortable with Zoanoids, many regarding them with pride. But they were still scary ass looking bastards if you weren't prepared for the sight.

Jane spun around to face Leng, walking backwards with her thumbs hooked under her backpacks straps. "You should really consider it too Leng. The Red's were a decent alternative to starving or freezing to death, but it's not exactly a good long term commitment."

"You gotta be eighteen to enlist, that's still two years away for me. Besides you really think they want street urchins like us? They'd probably just send us off to the police or something."

Jane scoffed, still walking backwards. "Have you _seen_ some of the recruitment centers around? The people working there don't give a fuck who wants to sign up as long as they're physically fit. It's not like there's a warrant out for our arrest or anything. As for your age, I bet I can cobble together a decent enough set of credentials for ya that they won't care. We're orphans, and we've never been caught by the cops so they don't exactly have extensive files on us."

Before Leng could reply, he spotted a group of four people behind Jane, all wearing some form of blue.

"Well well, wha'da we have here?" The lead one called out, a black skinned teenager with his hands in his sweatshirts pockets. "A couple of Red's hornin' in on Blue territory."

Jane spun back around on her heel, and looked the group over. "Way to play up the stereotype guys. A bunch of blacks wandering around after dark to prey on people." Leng came to a stop beside her, carefully watching the group in front of them.

"Oh shut the fuck up you bitch! I think we all know what's about to go down!" He pulled out a switchblade and flicked it open. "Try to leave the redhead intact boys." He said right before lunging at Leng, hoping to catch him in the first strike.

Anticipating the move, Leng sidestepped the stab while spinning his left elbow straight into his nose, breaking it and knocking him unconscious with the brutal counter. As the dark skinned male fell backwards, Leng snatched the switchblade from his limp hand and stabbed it through another Blue member's arm as he punched at him. Leaving the knife embedded in the limb, Leng swung a back fist followed by a haymaker with the same arm straight at his jaw, while he cried out in pain, knocking out a few teeth while cutting his knuckles on the enamel.

While Leng handled his share of the fight, Jane had kicked one enemy straight between the legs before catching a punch across the cheek from his friend. Rolling with the attack Jane grabbed the still extended arm and yanked forward, pulling the man off balance. While he was stumbling forward, Jane twisted back around and punched him as hard as she could in the stomach, knocking the wind out of him and making his eyes bulge as he coughed. While he was stumbling back, clutching at his gut and bent double, Jane charged, slamming her right knee into his face and knocking him out cold. Putting her foot back on the ground, she twisted into a spinning heel kick that smashes into the temple of the first gangster nursing his groin and taking him out of the fight.

Looking around, Jane found Leng already done with his opponents, smirking at her.

"You actually got hit by one of these pricks? They couldn't even touch _me_."

Jane scoffed, rubbing at her injured cheek. "Well that's no surprise. Everyone knows that everyone from Asia knows kung fu."

"That's racist Jane." He said jokingly, blue eye's alight with humor.

A gunshot cracked through the air, followed by the two being showered by dust and bits of concrete as the wall next to them was given a new hole and the teens flinched downward. Looking for the source of the shot, they saw another three Blue gang members a block away, one of them holding the gun.

"Jesus fucking Christ, they have a gun!" The two quickly dashed away, down the sidewalk, the new Blue gang members in pursuit. "This way!" Jane turned into a garbage filled alleyway, quickly climbing over the chain link fence like she'd done hundreds of times before, Leng right behind her.

Taking a quick left, they found another fence in their way, this time a tall wooden one. One they wouldn't be able to jump over so easily. "Freaking fences!" Luckily, they'd dealt with such a thing in the past.

Leng didn't bother slowing down, just twisting around so his back would slam into the fence, his hands cupped low in front of him. Jane smoothly stepped on the makeshift step and Leng pushed her up so she could scramble to the top of the fence, rapidly spinning around to pull Leng up after her, using her own weight and gravity as a pulley. As they dropped to the ground, they could hear the pursuing gangsters just clambering over the chain link fence, shouting obscenities. The two silently crouched behind the wooden fence, listening to the voices argue before fading away as they gave up.

"So, that happened." Jane said as she rose, brushing off some of the cement dust from her hoodie and casually restarting the walk back to the apartment they called home.

"Yup." Getting attacked and chased by rival gangs wasn't exactly a new experience for them.

* * *

It didn't take long for the pair to reach the rundown apartment complex they lived. The place didn't even have functioning locks on most of the doors.

Entering the apartment, Jane un-slung her backpack as she made her way to her corner of the apartment, hoping the computer parts she'd scavenged hadn't broken during the scuffle.

"Thanks for comin' with Leng, I'll see ya later."

Leng hummed in agreement, already making his way to his own space.

Reaching her corner, Jane scowled at seeing one of her roommates messing with her corner. It wasn't much, just a futon, some magazines and her laptop, but it was _hers_.

"Oi, get away from my stuff Finch." Finch was a pale, black haired guy, a few years older than her and fancied himself a leader of their gang. He was competent enough for it she guessed, but the guy pissed her off with his arrogance. She didn't mind stealing from or scamming aliens, but he seemed to go out of his way to make things as miserable as possible for all the non Earth natives he found, and it'd gotten him in trouble more than once. "Laptops broken in case you hadn't noticed, so no, you can't use it for porn."

"Yea yea." He pushed himself away from the broken computer. "So what'd ya get? Enjoy your last run as a free woman before selling out to the _Alliance?_" Finch spat the word out like it was poison.

"Parts to fix the laptop. And as a matter of fact I did enjoy it." She said dryly. "Get out of my hair and maybe I'll have it running sometime soon."

Finch just huffed in annoyance, wandering off to do whatever it was he did. Jane didn't care, just so long as he wasn't bothering her.

Cracking her fingers, Jane pulled her laptop to her as she sat cross legged on her futon. "Now, let's see what we can do with you."

* * *

Several hours later found Jane sprawled across her futon haphazardly, lightly snoring with her laptop on the floor nearby, lights blinking merrily.

Her sleep is interrupted by a foot lightly kicking her. "Time to wake up Jane, or the food'll get cold."

Jane's sleep fogged mind idly recognizes the voice as Leng's, and she wearily swats at him, groaning in protest and turning on her side to continue sleeping.

Leng rolls his eyes. "Fine, I'll just eat your pancakes myself then. It's not often we have chocolate chips after all."

Jane quickly stumbles to her feet in a rush and manages to find the kitchen table nearly tripping herself into her seat with her excitement. "I knew there was a reason I liked you!" She said around a mouthful of chocolate deliciousness.

"Right, not like it could be all those times I saved your hide or anything."

"Course not." She readily agreed. "That would just be silly."

Leng chuckles, before taking a sip from his coffee mug. "So did you get your laptop running?"

Jane hums in affirmation around a mouth full of pancake, quickly fetching her computer. "And," She swallows. "I put together something for you too." Pushing the monitor open and waking the laptop, Jane tapped at the keys and spun it around to face Leng before taking another large bite of her pancakes.

Leng was now staring at what looked like a set of documentation with the name Kai Leng on it. His name. He was in no way an expert, but it looked official enough. "When did you put this together?" He scrolled through the documents, noting the modified date of birth.

Jane looked at the clock in the bottom right corner of the computer; 8:27 AM. "About three and a half hours ago. The parts we got from the junkyard worked pretty well. Just had to clean 'em up a bit and switch 'em in and it was good to go. I was serious ya know. You should really think about signing up too."

He shrugged noncommittally, eyeing the fake documents. "Hmm, I'll think about it." A smirk crosses his face. "Maybe things'll be more fun around here without the resident nerd."

Jane snorts in amusement. "Yea? Well I think your tune'll change real quick the next time the coffee maker breaks and I'm not around."

Leng actually pauses mid sip as his eyes narrow in consternation. "…I hadn't thought of that."

"That's right you didn't! Who's the nerd now?" Jane chuckles, leaning her chair on its back legs.

"Still you." He assures her playfully.

She snorts in laughter, grinning back at her friend. If there's anything she'll miss here it'll be Leng. But she's already made her decision. She wants more than this dead end existence.

"I'm going to the recruitment center today, first thing after I finish eating. I'll leave the laptop with you. I made sure all the hacking software was installed right on the new hard drive, and you know how to work it." The beat up old thing had been very valuable when they wanted to break into places for a little theft. "I won't be needing it anymore, and I copied your fake documents onto an OSD in case you change your mind." The whole point of even fixing the laptop last night was so she could forge those documents, and make sure one of the gangs, and therefore Leng's means of surviving was still available after she'd left.

"Thanks Jane…" Leng says quietly, staring at the monitor contemplatively.

Jane takes her time finishing the last of her pancakes, but is soon out the door with nothing but the clothes on her back and a parting fist bump.

"_Look out galaxy. Here comes Jane Shepard."_

* * *

**End Chapter!**

**First off, wow, I seriously didn't think this guy would get so much attention, but it is a very pleasant surprise. Thanks to everyone who favorited and followed, especially for those of you kind enough to leave reviews, they really make my day!**

**The chapter's shorter than I wanted it to be, but I couldn't figure out how to continue it while maintaining the fluidity. I promise, there will be longer chapters in the future.**

**For those of you asking for specific pairings, I have thoughts, ideas and possibilities bouncing around, but I'm not even sure that I'll get to it in this fic. It might not be until the sequel that I actually make a pairing, if at all. (If things go well, I plan for this to be a trilogy, one fic for each game, not just one massive fic.)**

**Also I may have lied in the notes after the prologue. From the ideas I've been coming up with I think Shepard will be a lot closer to half and half for Paragon and Renegade behavior than I initially believed. Just a heads up.**

**Anyways, please let me know what you thought, all feedback, constructive criticism and questions welcome and appreciated!**


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